Officials estimated the fire had burned 824 acres as of about 5 p.m. Wednesday, and was only 25 percent contained.

Firefighters said the blaze started at 6 a.m. Monday and quickly burned 100 acres northeast of Beardsley Lake. By the afternoon, the blaze had grown to about 200 acres, according to a spokeswoman with the Stanislaus National Forest.

According to firefighters, the blaze is not threatening any power stations or residential areas.

It started along the eastern edge of Beardsley Lake and runs parallel to Highway 108, which remains open.

Fire crews are using air attack in addition to fighting the flames from the ground. They've called out additional resources to deal with the steep, rugged terrain.

So far, Tuolumne County Fire, Cal Fire and the U.S. Forest Service are all working to help put out the blaze.

The cause of the fire is under investigation.

Tuolumne County health officials told residents to limit their exposure to the smoky conditions. The fire is expected to burn for an extended period.

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